Composite shell with ceramic base

ABSTRACT

An explosive shell whose detonation is initiated by RF energy includes a ceramic spacer which separates, both physically and electrically, the two elements of the antenna and provides a mounting base and protection for the oscillator and associated components and wherein one element of the antenna is both led through the ceramic spacer and flushly disposed on the rear face of the spacer.

United States Patent Barnett [54] COMPOSITE SHELL WITH CERAMIC BASE [72] 'lnventor: Charles W. .BarnetQArlington, Va.

[73] Assignee: The Unlted States of America as I representedbytheSecretaryoltheArmy [22] Filed: May21,1910

[21] Appl.No.: 40,954

[52] US. Cl. ..l02/56, 102/702, 343/708 [51] Int-C1. ..F42c 13/04,F42b 13/12 [58] field ol Search ..102/56, 70.2, 70.2 P;

[ 1 References Cited UNITED STATES PATENTS 1,769,203 7/1930 Buckley "102/7021 [151 3,641,936 1 Feb. 15,1972

2,939,130 5/1960 RobinsonJr ..343/708 3,092,028 6/1963 Robinson, Jr ..l02/70.2P

Primary Examiner-Verlin R. Pendegrass Attorney-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and]. D. Edgerton I 1 s11 ABSTRACT An explosive shell whose detonation is initiated by RF energy includes a ceramic spacer which separates, both physically and electrically, the two elements of the antenna and provides a mounting base and protection for the oscillator and as sociated components and wherein one element of the antenna is both led through the ceramic spacer and flushly disposed on the rear face of the spacer.

12 Claims, 6 Drawing Figures IPATVEVNTEBFEB :5 ma

F/a/j CHARLES WABARN'ETT 7m g g 2 4 ATTORNEY theprojectile and target to v the proximity regulated.

includes a lead,

COMPOSITE SIIELL WITH CERAMIC BASE This invention relates generally to explosive projectiles and more particularly to small caliber shells adapted for control by telemetering or similar applications to induce detonation. I

Many types of explosive projectiles are known. Perhaps the most common types includes either a time fuze or an impact fuze. The effectiveness of explosive projectiles provided with such fuzes leaves'much to be desired, since the former type re lies upon an accurate setting of the fuze. timing mechanism while the latter type requires a direct hit in order to secure detonation. In either case, human judgment is required and,- even if a reliable determination is made, thenecessary time factor is a significant det ent particularly, for example, if the projectiles are of the antiaircraft type. Accordingly, efforts have been made to overcome the above-described objections by providing means involving automatically detonating the projectile fume in response to proximity of the target, and in this connection, numerous forms of proximity fuzes have been developed. Certain of these systems rely upon light waves or sound waves between initiate detonation of the projectile explosive charge at a point when the shell reaches a position within a predetennined range of the intended target. These latter described proximity detonated explosive shells have also been found to be unsatisfactory in certain respects, particularly in the case of explosive projectiles intended for use in antiaircraft operations, due to inflight vibrations which have been found in many instances to initiate a premature detonation of the fuse.

The present invention particularly relates to an arrangem'ent involving the use of radiofrequency energy for regulating the detonation of a projectile fuze. Such devices are in themselves well known; however, many of these prior known'proximity controlled shells are unsatisfactory in view of an extremely complicated mechanism for-the projectile fuze. Means are required for transmitting or radiofrequency waves between the in-flight projectile and the target and, in this respect, many prior known shells have incorporated various antenna arrangements provided throughout numerous different portions of the shell casing. The provision of thisantenna in the area of the nose .or

sidewall of the shell casing is well known in the art and per-' haps the most obvious shortcoming of such an arrangement is the susceptibility to accidental or careless handling prior to firing from the gun, which handling can very easily damage these antennas. It has been determined that a most effective composite shell may be provided by incorporating the antenna as an element located adjacent the base of the projectile casing suchthat, prior to firing,it is enclosed within the confines of the metal of the cartridge case and projectile casing and thus protected against many external forces. Before the present invention, it has not been possible to provide a satisfactory arrangement for a base-mounted antenna which could withstand the full pressure and temperature of the a telemetering arrangement for receiving and bulky structure necessary to provide Another object of the present invention is to provide an explosive projectile including a dielectric spacer fitted in its base and supporting a flush-mounted antenna.

Still another object of the present invention is to provide an "explosive projectile adapted to detonation by telemetering or similar applications and including an RF energy responsive antenna flush-mounted at the base thereof by means of a dielectric spacer of ceramic composition.

Another object of the present invention is to provide a composite shell including an antenna secured to a dielectric spacer which is press-fitted into the base of the shell casing.

A further object of the present invention is to provide a composite shell including an antenna printed upon the rear face of a ceramic'spacer projecting from the base of the shell casing and having a lead through joining the antenna with circuitry mounted upon the front face of the spacer.

Still further objects of the present invention will more readily appear as the nature of the invention is better understood. The invention consists in the novel construction, combination, and arrangement of parts hereinafter more fully described, illustrated and claimed.

Preferred and practical embodiments of the invention are shown in the accompanying drawing, in which:

FIG. I is a side elevation, partly in section, and illustrates a composite shell according to the present invention.

FIG. 2 is an end enlarged scale 3-3 of of a modified base-mounted an gmentary longitudinal sectional view of a modified base-mounted spacer with an antenna provided thereon. H

.FIG. 6 is a fragmentary longitudinal sectional view of still another embodiment of a base-mounted spacer having an anpresent invention will propellant charge wherein such an antenna would retain its full effectiveness throughout in-flight travel without any significant change in its electrical resistance.

By means of the present arrangement, an antenna system is provided which may be classified as a short asymmetric dipole with the shell casing serving as one element and a printed por 7 tion attached to a ceramic base on the shell providing the other element. The printed portion being an end loading, is arranged to serve both as an antenna and oscillator tank coil and through the ceramic base or with suitable circuitry such'as an oscillator, amplifier and power source which may be used to initiate the action of a fuze through a thyratron type of trigger, whichcomponents may be printed or otherwise mounted upon the inner face of the same spacer serving to support the printed antenna on'its rearface. 7

Accordingly, one of the primary objects of the present invention is to provide an improved composite shell having a base-mounted antenna.

spacer, joining semblies such that these tenna mounted thereon.

Similar referencecharacters designate corresponding parts throughout the several figures of the drawing.

' Referring now to the drawing,mor particularly FIG. I, the

be seen to comprise an explosive projectile generally designated casing 2 having'a nose 3 and base 4. The specific configuration of the casing 2, both as it applies to the exterior thereof as well as the inner cavity, is immaterial with respect to the present invention which re'sides more particularly in the combination of any well-known projectile casing and a ceramic disc supporting an antenna attached within an opening in the casing base. It will be understood that the interior of the casing base 2, in addition to containing a selected high-explosive charge (not shown), is provided with an opening within which is housed the required power supply 6 and amplifier and oscillator 7 associated with any suitable fuze assembly (not shown).

The concept of radio operated proximity fuze systems for high-explosive projectiles is well known in itself, and accordingly, it will be understood that any suitable fuze construction and related controlcomponents maybe provided in practicing the present invention. The provision of a concentric Y bore 5 adjacent the base-4 of the shell casing is intended to permit ready assembly of the illustrated necessary components which in turn maybe constructed of circular subasmay be easily installed from the rear of the casing and retained in a press-fit manner or by means of suitable adhesives.

Whatever the specific disposition present invention enables the provision of a base-mounted anor supportedupon a dielectric base member or spacer 9. In this connection, means are provided for permitting a rapid, inexpensive assembly of the basemounted antenna while at the same time insuring a secure elevation taken along the line 2-2 of FIG.

I, and includes a shell or projectile 5 in the base thereof of the power supply 6jand amplifier and oscillator 7, it will be understood'that the V necessary components into the shell, which would obviously lead to damaging of the fuse assembly and even the possible premature detonation of the high explosive.

The spacer 9 must exhibit several properties. It must be an inexpensive dielectric material capable of providing rigid support for the antenna structure on the exterior of the shell while at the same time electrically isolating the antenna from the metal shell casing. Additionally the spacer will be transparent to the RF radiation of the antenna. As previously indicated, an effective seal must exist between the juxtaposed surfaces of the spacer and the base 4 of the shell casing, which surfaces The antenna 8 may assume any of the several configurations upon the base or rear face 11 of the spacer 9, such as the spiral arrangement shown most clearly in FIG. 2 of the drawing or the form as shown by the antenna 80 of FIG. 4 comprising an open grillwork arrangement of fired on silver. In any instance, it will be understood that the silver antenna is deposited upon the face 1 l of the spacer with a size and design as specified by I the particular fuze'circuit involved in order that the design voltage requirements are met for'actuating the specific fuze assembly being utilized.

The ceramic spacer 9 illustrated in FIGS. l-3 will be seen to comprise a rear section 14 having an outer-exposed peripheral surface with a configuration adapted to provide a smooth must include a good electrical connection between the two components. The true test involves the capability of the spacer 9 to withstand the full heat and pressure or shock of the buming propellant (not shown) as contained in the metal cartridge case [0. Numerous tests have indicated that the only ceramic material capable of fulfilling all of the foregoing requirements is alumina, and then only certain alumina compositions have been found adequate for the present environment. The alumina must be of a fine grain, fine crystalline, and comprise a high-fired body of high tensile and compressive strength exhibiting great impact resistance. Inasmuch as a typical small caliber high-explosive shell may be subjected to a shock pressure from the propellant charge of upwards or in excess of 50,000 psi, it will be seen that a suitable alumina ceramic composition must have a compressive strength 'of at least 300,000 p.s.i. and a tensile strength of at least 50,000 psi. Alumina having these requirements is produced by several companies] such as the Carborundum Company; Centralab, Division of Globe Union, Inc., and the American Lava Company. Additionally, a composition produced by US. Stoneware under the product name Borundurri, has been successfully tested.

Extensive tests have indicated that a ceramic material as above described in the most preferred substance to be utilized and that other compositions such as those comprising plastics or glass fiber, are unsatisfactory. Several forms of ceramic dielectric spacers or bases 9, 9a or 9b are shown in the figures of the drawing. In each instance, it will be seen that a planar rear face I 1, 11a or 11b is provided on the rearmost end of the spacer, which face may include a diameter extending between the smaller diameter of the shell casing opening 5 and the larger diameter of the exterior of the casing base 4. The antenna 8 associated with the fuze assembly is attached to the rear face and preferably comprises a silver composition which is fused or fired on to the rear face and includes an antenna lead through 12 extending from the antenna 8 through a centrally disposed axial bore 13 in the spacer to the amplifier and oscillator 7 disposed within the shell casing opening 5 adjacent the A front face 19 of the spacer. The spacer is chamfered as at 9' in the area surrounding the axial bore 13 adjacent the rear'face I! to provide a relief for the passage of the lead through 12 from the transverse plane of the antenna 8 to the axial bore 13. During the attachment of the antenna and lead through to the spacer, a silver deposit 12a is also made to fill this relief area and thus effectively seal the rear of the bore l3 against the entrance of propellant gases.

Although components'of the required circuitry are shown in FIG. 1 as including separate elements 6 and 7 disposed within the shell casing opening 5, it will be understood that a more sophisticated and highly efficient arrangement is to install the directly upon the front face 19 of the spacer 9. The circuitry may thus be applied as a planar module C comprising either printed circuitry or thick film mounted directly directly on the spacer front face 19 and communicating with the forward portion of the lead through 12. Accordingly, it will be appreciated that the final assembly of a projectile will be greatly facilitated by providing for the preassembly of the ceramic spacers together with the antenna 8, lead through 12 and circuit module C whereupon this subassembly may then be press-fitted into the shell easing 2 in a single operation.

transition or continuity with the adjacent outer surface of the base 4 of the casing 2. Extending from the rear section 14 is a forward section l6 having a reduced diameter attaching surface 17 which intersects the radially projecting shoulder 18 formed on the rear section. The attaching surface 17 preferably comprises a straight cylindrical wall and terminates at its forward portion adjacent'the planar front face 19. The enlarged view of FIG. 3 most clearly illustrates the provision of a concave fillet 20 at the intersection of the front face 19 and lateral attaching surface 17 as well as a convex fillet 21 formed at the intersection of the surface 17 and shoulder 18 for reasons which will become obvious hereinafter.

Prior to assembly of a spacer having theantenna 8 provided on the rear face 11 thereof and a circuit module C'on its face, the coacting surfaces of the spacer 9 and shell base 4 must be prepared to insure a proper fit and secure attachment of the spacer to the shell. The periphery of the casing opening 5 in the area of the base 4 is machined to provide an interference fit of 0.003 inch between the surface of the opening 5 and the attaching surface 17 of the spacer.

Generally, an interference greater than 0.004 inch results in a tendency for thespacer to broach the shell and fails to provide any greater retaining action between the two com ponents, while making the interference less than 0.003 inch reduced the'retaining actiomwith any selected interference,

it will beunderstood thatthe amount of the retaining action is regulated by the rate of acceleration employed during pressing of the spacer into place. As an example, with a rate of 0.l inch/minute, the force required to pull the spacer from the shell base is of the order of l,500 pounds. Accordingly, with a higher rate a greater force would be required;

The attaching surface 17 of the spacer 9 is preferably coated with a 0.0005-inch thick layer S of pure silver which is fired on to the spacer surface and provides a twofold objective, namely, to act as a lubricant during the pressfitting of the components and also to provide a seal and to serve as an electrical connection between the two components. It will be appreciated that the foregoing construction assists in the provision of a gastight positive connection between the two components. The previously described fillets 20 and 21 will be seen to facilitate the press-fitting of the components together as the leadingmost concave fillet 20 will preclude any tendency for the attaching surface 17 to broach the juxtaposed inner surface of the opening 5, while the other fillet 21 will assist in enhancing the sealing between the rear edge of the shell base 4 and the shoulder 18 of the spacer. As shown in FIG. 1, a chamfer 22 may be provided at the intersection of gasket will he rarely necessary.

In the embodiments illustrated in FIGS. 5 and 6, modified ceramic spacers 9a and 9b are shown in the installed position within the base portion of a shell casing. In both of these instances, the body of the spacer is more or less rectangular in cross-sectional configuration as viewed in these figures of the drawing, and the front face or 19b thereof is each of a diameter no less than the diameter of the opposite rear face 11a or llb. In each of these latter cases, the base of the shell casing 2 is modified to provide a counterbore yielding a rearwardly facing shoulder or bottom stop 23 and an inwardly facing sidewall 24. The thus produced counterbore will be seen to cuit module C. Likewise,

between the serve as a seat for the forward portion of the selected spacer 9a or 9b which is press-fitted into the illustrated positions and may include the above-described teachings in connection with proved antenna mounting is provided comprising a ceramic spacer press-fitted into the rearopening of a metal projectile to provide both electrical and physical separation of two elements of an antenna, one of which is flush-mounted upon the rear face of the spacer in a transverse plane disposed to the rear of the shell casing base.

I claim:

1. An explosive projectile adapted to be detonated by RF energy comprising, a metal shell casing having a base provided with a rearwardly directed opening, a dielectric spacer mounted within said'base opening and including a rear face disposed in a plane transverse to the longitudinal axis of said shell casing and a front face positioned within said base opening,'said projectile including an asymmetric dipole antenna system, said shell casing comprising one element of said antenna system, an antenna mounted upon said dielectric spacer rear face, said spacer provided with a bore from said rear face to said front face, a lead through in said-spacer bore having its rearward portion joined to said antenna on said rear face whereby said antenna and lead through comprise the other element of said antenna system, and circuit means within said shell casing opening joined to the forward portion of said lead through adjacent said spacer front face.

2. An explosive projectile according to claim 1 wherein,

said spacer comprises a ceramic composition.

3; An explosive projectile according to claim 1 wherein, said antenna includes a printed member fused upon said spacerrcarface. v

4. An explosive projectile according to claim 1 wherein,

said spacer comprises an integral member having forward and rear sections, an attaching surface on the periphery of said front section, and said attaching surface embraced by said shell casing base with said spacer rear section disposed rearwardly of said base.

5 An explosive projectile according to claim 4 wherein,

said spacer is cylindrical and said rear section is of a greater diameter than said forward section.

6. An explosive projectile according to claim 4 wherein, said spacer is cylindrical and said rear section is of a diameter different than that of said forward section.

7. An explosive projectile according to claim 1 wherein, said circuit means is attached to said spacer front face.

8. An explosive projectile according to claim 7 wherein,

' said circuit means includes printed circuitry.

9. An explosive projectile according to claim 7 wherein, said circuit means includes thick film.

10. An explosive projectile according to claim 1 wherein, the interface between said spacer and shell casing base includes an electrically conductive layer. I

11. An explosive projectile according to claim 10 wherein, said layer comprises fused silveron said spacer.

12. An explosive projectile according to claim 3 wherein, said printed antenna is in the form of a spiral. 

1. An explosive projectile adapted to be detonated by RF energy comprising, a metal shell casing having a base provided with a rearwardly directed opening, a dielectric spacer mounted within said base opening and including a rear face disposed in a plane transverse to the longitudinal axis of said shell casing and a front face positioned within said base opening, said projectile including an asymmetric dipole antenna system, said shell casing comprising one element of said antenna system, an antenna mounted upon said dielectric spacer rear face, said spacer provideD with a bore from said rear face to said front face, a lead through in said spacer bore having its rearward portion joined to said antenna on said rear face whereby said antenna and lead through comprise the other element of said antenna system, and circuit means within said shell casing opening joined to the forward portion of said lead through adjacent said spacer front face.
 2. An explosive projectile according to claim 1 wherein, said spacer comprises a ceramic composition.
 3. An explosive projectile according to claim 1 wherein, said antenna includes a printed member fused upon said spacer rear face.
 4. An explosive projectile according to claim 1 wherein, said spacer comprises an integral member having forward and rear sections, an attaching surface on the periphery of said front section, and said attaching surface embraced by said shell casing base with said spacer rear section disposed rearwardly of said base.
 5. An explosive projectile according to claim 4 wherein, said spacer is cylindrical and said rear section is of a greater diameter than said forward section.
 6. An explosive projectile according to claim 4 wherein, said spacer is cylindrical and said rear section is of a diameter different than that of said forward section.
 7. An explosive projectile according to claim 1 wherein, said circuit means is attached to said spacer front face.
 8. An explosive projectile according to claim 7 wherein, said circuit means includes printed circuitry.
 9. An explosive projectile according to claim 7 wherein, said circuit means includes thick film.
 10. An explosive projectile according to claim 1 wherein, the interface between said spacer and shell casing base includes an electrically conductive layer.
 11. An explosive projectile according to claim 10 wherein, said layer comprises fused silver on said spacer.
 12. An explosive projectile according to claim 3 wherein, said printed antenna is in the form of a spiral. 